Field mapping is a major aspect of geological investigations. It is a geologic trip aimed at exposing the students to the application of their theoretical knowledge in the identification, measurement and interpretation of geologic structures due to natural phenomena; hence, the field
work bridges the gap between the theory in the classroom and the appreciation of rocks in their natural geological settings.
The field mapping was carried out in Nasarawa state within the North central Nigeria which are predominantly of Basement rocks (Igneous and metamorphic rocks of complex structures and characteristics).
The rock units of the Basement complex are of Precambrian era. The Precambrian Basement complex rocks of Nigeria cropping out in Northcentral Nigeria show predominant structural trends of N.S. These rocks include migmatites, Gneisses and schist which have been dated Archean to pan-African age. These were intruded by the older granites which are pan-African in age.
Intrusive granites of Jurassic age with cross-cutting contacts against older rocks referred to as the younger granites were also found. Other intrusions characterizing the Northcentral Basement complex of Nigeria include Trachytic/Rhyolitic dyke, pegmatitic dyke and also quarts dyke.
Veinlets which are either continuous or discontinuous in most cases, trends of foliations, the altitude (Strike, dip direction and dip amount) of the rocks were carefully measured alongside with the mineralogical characteristics of the various rocks observed within the Basement, their textures and conformability of some of the geologic structures.
The contacts of sedimentary to Basement were critically observed within the area of the ring dyke.
Aims and Objectives
The objectives of the field trip is to:-
- Expose students of Geology to practical academic experience and letting them get in touch with the lithologies, structures and complex nature of the Nigerian Basement rocks, so as to relate the field experience to the theoretical works for easy understanding and interpretation.
- To make the students to understand that the Basement is a lost for most of the solid mineral resources, industrial minerals/rock aggregates.
- The sedimentary-Basement contact, the structural characteristics and composition of the Basement complex studied so as to detect the structures, and their responsible field measurements taken by the students, equip the students with the knowledge and experience for the task ahead in carrying out their professional duties.
- It provides the students with the opportunity of interacting with people of various ethnic group within the mapped area.
LOCATION AND ACCESSIBILITY
The studied area is bounded by the sediments of the Sokoto and chad basin in the North, and it is bounded by the sediments of Niger and Benue Rivers in the south. It is located at latitudes of about 8O37.741 N to 8.56.3891N and longitudes of 747.151E to 80 39.4661E.The major towns within the studied area are Lafia, Akwanga and Keffi. Some of the villages within the mapped area are madda, mante, Agbonju, Wowyen and shamage.
The studied are was accessed through Abakaliki-Enugu express way to Enugu. The trip continued from Enugu town through 9th mile to Nsukka to Oboloafor and to Otukpa in Benue state to Markurdi, and to Lafia in Nassarawa state Across River Benue. The journey continued from Lafia to Akwa-nga, our lodge.
On the field map, proper, accessibility was through Akwanga-Lafia road, Akwanga-Wamba road, Akwanga-Keffi road and finally Keffi-Laminga-Nassarawa road.
Climate and Rainfall
The mapped area is situated in the savannah belt of West Africa with wet season from May to September, accompanied by a long dry season from October to April. The Northeast trade wind keeps the humidity extremely low from November to early March. There is general warm temperature in the day and relatively cold at the night.
vegetation and Topography (Field mapping)
The studied area possess moderated vegetation which are sparse in few areas, despite that it is mainly of igneous and metamorphic complexes. There are still some areas of sedimentary deposits which are a bit thickly vegetative following easy release of plant nutrients for use.
On the soil type, the areas not covered by the Basement are covered by day-loamy soil thereby giving the inhabitants the opportunity to cultrate crops such as rice, yam, and other cereal crops.
The topography of the Northcentral Nigeria are mainly plain and some plateaux due to series of basement uplifts.
Due to occurrence of rainfall the rains find their routes to streams, and rivers which are scattered around. The drainage system is from the highland to the lowlands, and to the streams. The rivers in the area include made river, River Kwoi, Missouri river, all of which drain into River Benue.
People and Culture
The major challenge encountered in the course of the study is poor accessibility of the studied locations.